| Río San Juan | |
| Settlement Type: | Department |
| Subdivision Type: | Country |
| Subdivision Name: | Nicaragua |
| Seat: | San Carlos |
| Seat Type: | Capital |
| Area Total Km2: | 7543 |
| Population As Of: | 2021 estimate |
| Population Footnotes: | [1] |
| Population Total: | 137189 |
| Population Density Km2: | auto |
| Population Urban: | 36965 |
| Blank Name: | ISO 3166-2 |
| Blank Info: | NI-SJ |
Río San Juan (pronounced as /es/) is a department in Nicaragua. It was formed in 1957 from parts of Chontales and Zelaya departments. It covers an area of 7,543 km2 and has a population of 137,189 (2021 estimate). The capital is San Carlos. The department also includes the Solentiname Islands archipelago and the San Juan River, after which it is named. Trinidad, in Río San Juan, is the most southerly point in Nicaragua.